The present invention relates to a floppy disk driving apparatus, particularly to a circuit which generates a disk change signal for detecting existence of a floppy disk inserted thereto.
A known conventional floppy disk driving apparatus has an index sensor which detects the rotation of the floppy disk and a disk-in sensor which detects the insertion state of the floppy disk. FIGS. 1B and 1A show schematic diagrams of the index sensor and disk-in sensor, respectively, of a conventional floppy disk driving apparatus.
Referring to FIG. 1A, when a floppy disk is inserted into a floppy disk driving apparatus, light-receiving transistor PQ1 is turned off, thereby cutting off light emitted from the light emitting diode PD.sub.1 of the disk-in sensor S1. If light-receiving transistor PQ1 is turned off, a logic signal of line 1 becomes a high level signal and then the high level signal is applied to the clear terminal of flip-flop FF.sub.1.
A disk change reset signal is applied from a controller (not shown) to the clock terminal CL of the flip-flop FF.sub.1, whereby flip-flop FF.sub.1 outputs the logic "high level signal" through the output terminal Q of the flip-flop FF.sub.1, thus enabling the controller to detect the insertion state of the floppy disk. By detecting the logic high level on the disk change signal line, the controller determines that the disk has been changed and thereby can operate the floppy disk driving apparatus under a normal condition.
When the floppy disk is extracted from the floppy disk driving apparatus, the disk-in sensor S1 is activated and a logic "low level signal" is output through line 1, thereby the output signal of a logic "low level signal" is applied to the clear terminal CLR of the flip-flop FF.sub.1 and then the flip-flop is cleared. A logic "low level signal" is then output through the output terminal Q of the flip-flop FF.sub.1. When the disk change signal from the output terminal Q of the flip-flop FF.sub.1 becomes a logic "low level signal", the controller detects an extraction of the floppy disk.
Referring to Fig. 1B which is a circuit for detecting a rotation of the floppy disk, an index sensor S2 is activated by the rotation of the floppy disk, whereby an index sensing circuit 10 detects an index pulse. Conventional floppy disk driving apparatus as shown in FIGS. 1A and 1B comprises both the disk-in sensor and the index sensor; consequently, the design of a conventional floppy disk driving apparatus is complex and material cost of the apparatus is high.